Alkaline bright zinc plating

ABSTRACT

Non-cyanide, alkaline electroplating baths for bright zinc plating containing quarternized polymeric condensates of alkylene polyamines and 1,3-dihalo-2-propanol as grain refiners preferably in admixture with aldehyde type brighteners and mercapto substituted heterocyclic compounds capable of producing the bright, fine grained deposits over a broad current density range.

United States Patent [1 1 Duchene et al.

[451 May 27, 1975 [541' ALKALINE BRIGHT ZINC PLATING [75] Inventors:Joseph R. Duchene, Southfield,

Mich.; Philip J. De Christopher, Chicago, Ill.

[73] Assignee: Richardson Chemical Company, Des

Plaines, I11.

[22] Filed: Sept. 24, 1973 [211 App]. No.: 400,427

[52] U.S. Cl 204/55 R; 204/DIG. 2 [51] Int. Cl. C23b 5/10; C23b 5/46[58] Field of Search 204/55 R, 55 Y, 43 Z, 44,

[56] References Cited UNITED STATES PATENTS 3,317,412 5/1967 Dahlmann204/55 R 3,655,534 4/1972 Kampe 204/55 R 3,672,971 6/1972 Senge et al204/55 R 3,803,008 4/1974 Rosenberg et al. 204/55 Y 3,823,076 7/1974Rushmere 204/55 R Primary Examiner-G. L. Kaplan Attorney, Agent, or Firm-Alan M. Abrams [57] ABSTRACT sity range.

30 Claims, No Drawings ALKALINE BRIGHT ZINC PLATING This inventionrelates to zinc electroplating and more particularly to alkaline brightzinc electroplating conducted in an aqueous bath free from cyanides.

Zinc electroplating has conventionally been conducted in a plating bathemploying alkali metal cyanide salts such as sodium cyanide as acomplexing agent to achieve the desired plating operation and to producebright, smooth grained zinc deposits. However, because of the toxicityof cyanides and more recently because of the environmentalconsiderations adversely affecting the economic employment of thesecyanides other plating methods have been sought which avoid and do notrequire the use of these cyanide salts.

A wide variety of procedures and additives have been suggested for usein zinc plating for the purpose of avoiding cyanides. Most of theseemploy an alkaline plating bath system utilizing an alkali metal orsodium zincate combined with additives to achieve the desired brightzinc deposit with a smooth or fine grained, mirror-like surface.Foremost of these various additives which have been suggested andemployed in these highly alkaline bath systems are materials generallyclassified as polyamines, and especially the relatively simplepolyamines such as alkylene diamines for example ethylenediamine whichreportedly serve as complexing agent replacements for the cyanide salts.These polyamines are usually employed with a variety of other additivesconventionally employed in zinc plating, for example, grain refiners,brighteners and throwing agents.

While these alkaline systems employing the polyamine type additives doavoid the use of substantial amounts of cyanides, they generally havenot been overly successful, however, and the zinc plating depositstypically produced have a number of deficiencies such as a dull orgranular finish which render them of little comercial value. Suchsystems, moreover, typically also lack the desired capability ofproducing a suitable smooth, mirror-like plating deposit over a broadcurrent density range and generally are especially ineffective at thelower current density ranges conventionally used in commercial plating.In addition, a substantial number of these systems for effectiveoperation still require the presence of some cyanide, although at areduced concentration, which in effect only minimizes but does noteliminate the problems associated with the use of cyanide salts.

Various other alkaline bath systems have been suggested which alsoutilize polyamines although generally of more complex nature, andusually in polymeric form and/or interracted with other compounds suchas aldehydes andheterocyclic compounds, for example, a reaction productor a polyfheril": condensate of an alkylene polyamine and aepihalohydrin. While certain of these have been somewhat successful theygenerally suffer from one or more deficiencies in that the depositsobtained do not have the degree of brightness or luster desired or asmooth, fine-grained surface necessary for most commercial application.Moreover, certain of these systems generally are not capable ofproducing fine-grained, mirror-like deposits over a broad currentdensity range and more specifically at the low current density range offrom to to 40 amperes per square foot. This limitation or inability toachieve desirable plating over a broad current density rangesubstantially restricts the usefulness of these systems and generallylimits their application to plating objects which are relatively uniformin shape and configuration thus precluding their use in plating objectswhich are irregular or in barrel plating where the plating must beconducted over a broad current density range.

It has now been discovered, however, that certain quarternized polymericcondensates of alkylene polamines and 1,3-dihalo-2-propanol may beemployed in a non-cyanide zinc electroplating bath, typically also withbrighteners, to produce fine grained, bright deposits. It has beenfurther found that when such polymeric condensates are employed withcertain mercapto substituted heterocyclic compounds the desired bright,mirror-like deposit is achieved over a broad current density rangeincluding the critical low current densities.

Accordingly, an objective of this invention is to provide an alkaline,bright zinc plating bath which does not require or utilize cyanidesalts. Another object is to provide such a bath employing a quarternizedpolymeric condensate of an alkylene polyamine and a l,3-dihalo-Z-propanol capable of producing a smooth, finegrained deposit. Afurther object is to employ such polymeric condensate with brighteningagents to achieve bright, mirror-like deposits. A still further objectis to provide such a bath with the addition of certain mercaptosubstituted herterocyclic compounds capable of producing the bright,fine-grained Zinc deposit over a broad current density range. Stillanother object is to provide a method of zinc electroplating employingsuch improved bath and capable of effectively operating in acommercially desirable manner completely free of any cyanides. These andobjects of this invention will be apparent from the following furtherdetailed description thereof.

The electroplating of zinc in an aqueous alkaline bath is effected inaccordance with this invention by adding a quarternized polymericcondensate of an alkylene polyamine and a l,3-dihalo-2-propanol to suchbath so as to obtain smooth, fine-grained deposits. In general, thesepolymeric condensates are produced by reacting the alkylene polyamineand dihalopropanol in a con densation reaction to produce asubstantially uncrosslinked, aqueous soluble polymeric condensate. Inaccordance with this invention the polymeric condensate is employed as aquarternary salt which involves a further reaction of the polymericcondensate with a suitable quarternizing agent.

The dihalopropanols which may be interracted with the alkylenepolyamines include 1,3-dibromo-2- propanol; 1,3-diiodo-2-propanol or1,3-dichloro-2- propanol with the 1,3-dichloro-2-propanol beingparticularly preferred in most instances.

The alkylene polyamines which may be reacted with the dihalopropanolhave at least one tertiary amino group such as dimethylaminopropylamine(N,N- dimethylpropylenediamine), diethylaminopropylamine(N,N-diethylpropylenediamine), N-aminopropylmorpholine,dimthylaminoethylamine, diethylaminoethylamine,N-aminopropyldiethanolamine, or N- methyliminobispropylamine.

Other alkylene polyamines containing at least one tertiary amino groupand at least one secondary amino group may also be employed such asN,N-dimethyl-N'- methylpropylenediamine; N,N-dimethyl-Nmethylethylenediamine; or N,N-diethyl-N'- ethylethylenediamine.

Df the various alkylene polyamines which may be condensed with thedihalopropanol either alone or in admixture, the lower alkylenepolyamines. where the .alkylene bridge contains from 2 to 5 carbon atomsand where the tertiary amino group is substituted with alkyl groups offrom l to about 5 carbon atoms, are pre ferred particularly when thedihalopropanol is l,3- dichloro-2propanol with a particularly preferredalkylene polyamine being dimethylaminopropylamine.

In preparing the desired polymeric condensates for use in accordancewith this invention, the alkylene polyamine should be condensed with thedihalopropanol in a mol ratio of from about 0.5 to 1.75 mols of theamine per one mol of the dihalopropanol. Usually a more limited range ispreferred, however, and when employing the preferred1,3-dichloro-2-propanol the mol ratio of the polyamine to1,3-dichloro-2- propanol advantages ranges from about 0.8 to about l.5mols of polyamine to one mol of dichloropropanol. Usually thecondensation is effected according to conventional procedures over aperiod of about l to 3 hours with the temperature being maintainedbetween to 40C.

As indicated, the polymeric condensate employed in accordance with thisinvention to effect the grain refinement of the deposit is utilized as aquarternary salt. This quarternization may be effected according toconventional procedures and suitable quarternized agents for thepolymeric condensates are the lower alkyl halides such asmethyl-chloride, -bromide, or -iodide, ethyl-chloride, -bromide or-iodide, or alpha chloroglycerol, diloweralkyl sulfates such asdimethyl-, diethyldipropylor dibutyl-sulfates; lower alkyl esters ofaryl sulfonates such as methyl toluene sulfonate and methyl benzenesulfonate', alkyhalo esters such as ethyl-chloroacetate', alkylenehalohydrins such as ethylenechlorohydrin or alkylene oxides such asethylene oxide and propylene oxide.

While the polymeric condensates in accordance with this inventionproduce a grain refined or smooth deposit, such deposit is not usuallyof the brightness or luster desired in most instances and accordingly, apreferred embodiment of this invention is to employ brightening agentstogether with the polymeric condensate so as to produce both smoothgrained and bright deposits. These brighteners include those materialsconventionally employed in zinc plating and typically contain a carbonylgroup of aldehyde functionality which generally may be represented bythe formula wherein R and R are independently selected from the groupconsisting of hydrogen, alkyl of l to about 10 carbon atoms, aryl andheterocyclic oxygen and sulfur containing radicals and include, forexample, mhydroxy benzaldehyde, p-hydroxy benzaldehyde, piperonal.o-hydroxy benzaldehyde (salicylaldehyde), vanillin, veratraldehyde,benzaldehyde, B-methoxy propionaldehyde, furfural, glyceraldehyde andanisaldehyde, thiophene-Z-aldehyde.

Of the various aldehyde materials which may be employed, the arylaldehydes and particularly the benzaldehydes such as anisic aldehyde(pmethoxybenzaldehyde) or vanillin (p-hydroxy-mmethoxybenzaldehyde) orvarious combinations thereof are preferred. These aldehydes brightenersmay be employed in the bath of this invention as addition products withsuch materials as sodium bisulfite to increase their alkaline solubilityif desired.

Employment of these brightening agents in most instances substantiallyimproves the luster or brightness of the deposit. However, thisfrequently only occurs at the higher current density ranges generallyabove about 40 or more usually above about 20 amperes per square foot upto about to 200 amperes per square foot. In accordance with thisinvention, certain mercapto substituted heterocyclic compounds may beand are preferably employed in combination with the polymeric condensateand brightener so as to achieve the bright, fine-grained deposit over abroad current density range and particularly at the lower currentdensity ranges conventionally employed in most commercial platingoperations and generally below about 40 or more usually about 20 down toO amperes per square foot.

These mercapto substituted heterocyclic compounds employable with thepolymeric condensates and brighteners in accordance with this inventionmay generally be described as ortho mercapto substituted pyridines orpyrimidines, that is where the mercapto substituent is positioned on the2 ring carbon atom. These mercapto substituted pyridines or pyrimidinesmay be represented by the following general formula:

or the tautomers thereof wherein X is selected from the group consistingof N TI 4 wherein R is selected from the group consisting of hydrogen,hydroxy, mercapto and acyl and wherein R R and R are each independentlyselected from the group consisting of hydrogen, hydroxy, mercapto, acyl,amino, alkyl, carboxy and carbamoyl.

Examples of mercapto substituted heterocyclic compounds which may beemployed either individually or in admixture according to this inventionincludes pyridines, that is where X of the formula is CR andpyrimidines, that is, where the X is nitrogen. These compounds may besubstituted as indicated in the formula and where any of the various Rsubstituents is alkyl or acyl such substituents can contain from 1 toabout 5 and more preferably from 1 to 3 carbon atoms such as methyl,ethyl, or propyl or where acyl such groups as formyl, acetyl orpropionyl. Typical examples of these compounds include pyridines such asZ-mercaptopyridine;

2-mercapto-3-acetylpyridine;

2-mercapto-3-hydroxypyridine;

2,3-dimercaptopyridine; 2,3-dimercapto-6-acetylpyridine;

2-mercapto-4-hydroxypyridine; 2,4-dimercaptopyridine;2-mercapto-4,S-dihydroxypyridine; 2-mercapto-4-aminopyridine;2,6-dimercapto-3-acetylpyridine; 2-mercapto-5-methylpyridine;2-mercapto-5-aminopyridine; 2-mercapto-S-hydroxypyridine;2-mercapto-6-hydroxypyridine; 2-mercapto-6-carbamoylypyridine;2,6-dimercapto-3-carboxypyridine; or 2-mercapto-5,6-diethylpyridine; andpyrimidines such as 2-mercaptopyrimidine; 2,6-dimercaptopyrimidine;2-mercapto-4-aminopyrimidine; 2-mercapto-4,6-dihydroxypyrimidine;2-mercapto-4-ethylpyrimidine; 2-mercapto-4-hydroxy-6-methylpyrimidine;2-mercapto-6-acetylpyrimidine;2-mercapto-4-hydroxy-5,-diethylpyrimidine; 2,4-dimercaptopyrimidine; or2-mercapto-6-hydroxypyrimidine As indicated, the mercapto pyridines orpyrimidines represented by the above formula may also in many instancesexist in tautomeric or isomeric form. For example, one of the preferredcompounds according to this invention is 2-thiouracil and such compoundcan exist as 2-mercapto-4-hydroxypyrimidine or 2-thio-4- oxopyrimidineor as an intermediate tautomer as 2-thioxo-4-hydroxypyrimidine and2,4-dithiouracil can exist as 2,4-dimercaptopyrimidine or 2,4-dithiopyrimidine. All of these tautomeric compounds are accordinglyembraced within the compounds which may be used in accordance with thisinvention as represented by the above formula.

Of the various compounds which may be employed according to theinvention the preferred compounds are pyridines or pyrimidines of theformula where the mercapto group is substituted in the 2 ring positionand generally also with a hydroxy group in one of the 4 or 6 position.Within this preferred class of compounds the pyrimidines are especiallypreferred and examples of compounds having particular utility in thebath of this invention are 2-thiouracil and Z-mercapto 4,6-dihydroxypyrimidines.

The electroplating bath of this invention may be prepared and operatedin accordance with the general procedures conventionally employed foralkaline bright zinc plating. Typically the bath is prepared as anaqueous solution and rendered alkaline by the addition of a suitablealkaline material such as alkali metal hydroxide or carbonate forexample sodium or potassium hydroxide. The quantity of alkaline materialadded should be capable of dissolving the zinc compound employed as thesource of the zinc ion in the bath and generally should be in excess ofthat required to create the desired alkali metal zincate such as sodiumzincate as well as to maintain the pH of the solution alkaline andgenerally above 7 and preferably above 14.

The source of the zinc ion in the bath can be varied and generally anyof the zinc compounds; conventionally employed in alkaline bright zincbaths may be utilized. Typically such compounds include zinc salts oroxides such as zinc sulfate, zinc acetate or zinc oxide with the zincsulfate generally being preferred. The amount of zinc in the bath can bevaried depending upon the desired results and operating condition butgenerally is maintained within the range of from about 3 to about 15grams per liter.

The quantity of the quarternized polymeric condensate utilized in thebath will in general be a function of the particular brightener andmercapto substituted compound employed as well as the particularpolymeric condensate utilized. Typically, however, when employingpolymeric condensates of such alkylene polyamines asdimethylaminopropylamine and [,3- dichloro-2-propanol, the quantity ofthe condensate in the bath should range from about 0.25 to about 5 gramsper liter with a more limited range of from about 0.3 to about 0.75grams per liter being preferred especially when used in combination withthe preferred mercapto compounds.

The quantity of the mercapto substituted compound employed in the bathin similar fashion is also interrelated to the specific polymericcondensate and aldehyde brightener employed as well as the particularmercapto substituted compound or combination of compounds utilized.Generally, however, the mercapto compound is maintained in the bathwithin the range of from about 0.01 to about 0.2 grams per liter with amore limited range being preferred of from about 0.025 to about 0.075grams per liter particularly when employing such preferred mercaptocompounds such as 2-thiouracil or 2-mercapto-4,6- dihydroxypyrimidine.

The brighteners used in combination with the quarternized polymericcondensate typically will be present in the bath within the rangesconventionally utilized for alkaline zinc plating baths. Typically thiswill range from about 0.1 to about 5 grams per liter with a more limitedrange from about 0.2 to about 0.5 grams per liter being moreadvantageously employed particularly when employing the preferredbenzaldehyde-type brighteners.

The electroplating of zinc conducted in accordance with the method ofthis invention is effected in conventional fashion basically by passinga direct current from a zinc anode through the aqueous alkaline,noncyanide bath of this invention containing essentially the polymericcondensate, brightener and mercapto substituted compound to the desiredcathode article which is to be electroplated with the zinc. This methodmay be conducted at temperatures from about 60 to about 100F. Thecurrent densities employed may range from above 0 to about 200 amperesper square foot with a more limited range of from about 0.5 to aboutamperes per square foot being satisfactory for most plating operations.

The plating bath of this invention may contain further additives of thetype conventionally employed in alkaline zinc electroplating baths andincludes such materials as polyvinyl alcohols, gelatine, polyetheralcohols, polyesters, glue and peptone. Of these various materialspolyvinyl alcohol or its various derivatives are especially preferredand appear to greatly enhance the mirror-like deposits of the platingsproduced in accordance with this invention. When so employed, thesepolyvinyl alcohols should be utilized in the bath within a range of fromabout 0.02 to about 0.2 grams per liter.

The following examples are offered to illustrate the plating bath andelectroplating methods of this invention.

EXAMPLE I Ouarternized polymeric condensates of the type employablc inthe electroplating bath of this invention may be prepared as follows:

Into a 1 liter. 4-neck. round bottom flask (equipped with a mechanicalstirrer. thermometer, condenser. and a pressure-equalized additionfunnel) were placed 877 grams (0.859 mol) of dimethylaminopropylamineand about 165 grams of di-ionized water. The mixture was stirred withcooling to about 2025C. While maintaining this temperature. 100.0 grams(0.775 mol) of 1.3-dichloro-2-propanol were added dropwise over a onehour period with stirring. Then the mixture was stirred for anadditional 0.5 hour below 30C to form a prepolymer mixture which wasslightly cloudy. but homogeneous. pale yellow liquid having a pH of 5-6.

Exactly 383.7 grams of the pre-polymer mixture together with about 200ml. of de-ionized water, and 38.8 grams (0.969 mol) of sodium hydroxidepellets were mixed to form a basicified pre-alkylation mixture with a pHabout 9 and added to a 2 liter stainless steel Paar pressure vessel. Thevessel was sealed, and about 60 grams of gaseous methyl chloride weremetered into the vessel over a 4 hour period at about 50-70 p.s.i.g.

while maintaining the temperature at between 8792C. The pressure vesselwas then cooled and discharged revealing an effervescent. slightlyclouded tanprange solution. Using about 75 ml. of de-ionized water. thisproduct material was quantitatively transferred from the vessel andfiltered to yield 875.3 g. of aqueous polymer with a pH of about 6 and33.3 weight percent solid content. A material balance indicated that thepre-polymer had only taken up 45.2 grams (0.895 mol) of themethylchloride provided. The mol ratios of reactants in this preparationtherefore were dimethylaminopropylamine 1.0 mol; 1.3-dichloro-2-propanol0.90 mol; sodium hydroxide 1.13 mol and methyl chloride 1.04 mol.

EXAMPLE II A series of aqueous alkaline. non-cyanide zinc electroplatingbaths were prepared to zinc plate Hull test panels. The plating wasconducted in a standard Hull cell (267 ml) with the Hull cell panel ineach test connected as the cathode of the bath. The plating wasconducted at an operating current of 1 ampere represetning a currentdensity range on the test panel varying from a high range of from about40 to about 60 am peres per square foot (a.s.f.) and a low range of fromabout 0.2 to about 0.5 (a.s.f.). The plating time was about 10 minuteswith the bath being maintained at a temperature of about 70F. The bathin each run had the components and concentrations as shown in Table lwith the results summarized in Table 11.

TABLE I CONCENTRATION IN TABLE I-Continued CONCENTRATION IN COMPONENTGRAMS PER LITER polymeric condensate I l heterocyclic compound (2) 0.05

( l polymeric condensate as prepared in Example I diluted with water tomake a solution of approximately 5.8 weight percent solids. (2)Z-thiouracil in combination with I grams/liter of NnOH forsoluhilivution.

was semi-bright to mirror bright with the semi-bright deposits appearingat the lower current density range of from 0 to 10 a.s.f. and the mirrorbright at the higher ranges.

3 The plating was similar to test 2 except the mirror bright deposit nowextended over the entire current density range.

As may be observed from the results summarized in Table II, the additionof the polymeric condensate of this invention produced a grainrefinement of the zinc deposit and the further addition of the mercaptosubstituted compound extended the brightening effect of the brightenerover the entire current density range.

We claim:

1. A bright zinc, cyanide-free electroplating bath comprising an aqueousalkaline solution containing a source of zinc ions, and from about 0.25to about 5 grams per liter of a quarternized polymeric condensate of analkylene polyamine having at least one tertiary amino group and a1,3-dihalo-2-propanol where the mol ratio of the polyamine to thedihalo-propanol ranges from about 5.0:1 to 1.75:1, respectively.

2. The electroplating bath of claim 1 wherein the bath contains fromabout 0.1 to about 5 grams per liter of an aldehyde brightener.

3. The electroplating bath of claim 2 wherein the bath contains fromabout 0.01 to about 0.2 grams per liter of a heterocyclic compound ofthe formula:

or tautomers thereof wherein X is selected from the group consisting ofN and C-R where R is selected from the group consisting of hydrogen,hydroxy, mercapto and acyl; R R and R are each independently selectedfrom the group consisting of hydrogen, hydroxy, mercapto, acyl. amino,alkyl, carboxy and carbamoyl.

4. The electroplating bath of claim 3 wherein the beterocyclic compoundis 2-thiouracil.

5. The electroplating bath of claim 3 wherein the heterocyclic compoundis 2-mercaptopyrimidine.

6. The electroplating bath of claim 3 wherein the heterocyclic compoundis 2,4-dimercaptopyrimidine.

7. The electroplating bath of claim 3 wherein the heterocyclic compoundis 2-mercapto-4-amino-6- hydroiiypyrimidine.

8. The electroplating bath of claim 3 wherein the heter'ocyclic compoundis 5-carboxy-2-mercaptopyridinc.

9. The electroplating bath of claim 3 wherein the heterocyclic compoundis 3-hydroxy-2-mercaptopyridine.

10. The electroplating bath of claim 3 wherein the heterocyclic is2-mercapto-4,6,-dihydroxypyrimidine.

11. The electroplating bath of claim 3 wherein the heterocyclic compoundis 2-thiouracil and the aldehyde is a mixture of anisic aldehyde andvanillin.

12. The electroplating bath of claim 3 wherein the heterocyclic compoundis 2-mercapto-4,6- dihydroxypyrimidine and the aldehyde is a mixture ofanisic aldehyde and vanillin.

13. The electroplating bath of claim 2 wherein the brightener is analdehyde having the formula wherein R and R are independently selectedfrom the group consisting of hydrogen, alkyl, aryl and heterocyclicoxygen and sulfur containing radicals.

14. The electroplating bath of claim 13 wherein the aldehyde brighteneris a benzaldehyde.

15. The electroplating bath of claim 13 wherein the aldehyde isvanillin.

16. The electroplating bath of claim 13 wherein the aldehyde is anisicaldehyde.

17. The electroplating bath of claim 13 wherein the aldehyde isp-hydroxy-benzaldehyde.

18. The electroplating bath of claim 1 wherein the bath contains fromabout 0.01 to about 0.2 grams per liter of a heterocyclic compoundselected from the group consisting of a 2-mercapto substituted pyridineor pyrimidine.

19. The electroplating bath of claim 18 wherein the polymeric condensateand heterocyclic compound are present in the bath with the ranges offrom about 0.3 to about 0.75 and from about 0.025 to about 0.075 gramsper liter, respectively.

20. The electroplating bath of claim 1 wherein the source of the zincions is a water soluble zinc salt.

21. The electroplating bath of claim 20 wherein the zinc salt is zincsulfate.

22. The electroplating bath of claim 1 wherein in the polymericcondensate the dihalopropan'ol is L3- dichloro-2-propanol.

23. The electroplating bath of claim 1 wherein in the polymericcondensate the alkylene polyamine has a tertiary amino group substitutedwith alkyl groups of from 1 to 5 carbon atoms and the alkylene bridgecontains from about 2 to about 5 carbon atoms.

24. The electroplating bath of claim 1 wherein in the polymericcondensate the alkylene polyamine is dimethylaminopropylamine.

25. The electroplating bath of claim 1 wherein in the polymericcondensate the alkylene polyamine is dimethylaminopropylamine and thedihalopropanol is 1.3- dichloro-2-propanol and the mo] ratio of thepolyamine to the 1,3-dichloro-2-propanol ranges from about 0.8:1 toabout 1.5:1, respectively and the condensate is substantiallyuncrosslinked.

26. The electroplating bath of claim 1 wherein the polymeric condensateis present in the bath within the range of from about 0.3 to about 0.75grams per liter.

27. The electroplating bath of claim 1 wherein the bath contains apolyvinyl alcohol within the range of from about 0.02 to about 0.2 gramsper liter.

28. The electroplating bath of claim 1 wherein the pH is above 14.

29. In a process for the electroplating of zinc the improvementcomprising effecting the electroplating with the alkaline bath of claim1 free from any cyanide.

30. The process of claim 29 wherein the plating is conducted at atemperature of from about 60 to about F and at a current density of upto 200 amperes per square foot.

Patent No. 3,886,05 Dated May 7, 975

Inventor(s) Joseph R. Duchene and Phillip J. DeChristopher It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column l, line 16 "R should be deleted and "and C-RM' inserted in itsplace.

Column 8, line 39 "5.0" should be deleted and "0.5" inserted in itsplace.

[SEAL] Arrest:

RUTH C. MASON .4 m'sling ()j'j'iver C. MARSHALL DANN ('mmnisximu'rnflalvnls and Trmlz'murkx

1. A BRIGHT ZINC, CYANIDE-FREE ELECTROPLATING BATH COMPRISING AN AQUEOUSALKALINE SOLUTION CONTAINING A SOURCE OF ZINC IONS, AND FROM ABOUT 0.25TO ABOUT 5 GRAMS PER LITER OF A QUARTERNIZED POLYMERIC CONDENSATE OF ANALKYLENE POLYAMINE HAVING AT LEAST ONE TERTIARY AMINO GROUP AND A1,3-DIHALO-2PROPANOL WHERE THE MOL RATIO OF THE POLYAMIDE TO THEDIHALOPROPANOL RANGES FROM ABOUT 5.0:1 TO 1.75:1, RESPECTIVELY.
 2. THEELECTROPLATING BATH OF CLAIM 1 WHEREIN THE BATH CONTAINS FROM ABOUT 0.1TO ABOUT 5 GRAMS PER LITER OF AN ALDEHYDE BRIGHTENER.
 3. Theelectroplating bath of claim 2 wherein the bath contains from about 0.01to about 0.2 grams per liter of a heterocyclic compound of the formula:4. The electroplating bath of claim 3 wherein the heterocyclic compoundis 2-thiouracil.
 5. The electroplating bath of claim 3 wherein theheterocyclic compound is 2-mercaptopyrimidine.
 6. The electroplatingbath of claim 3 wherein the heterocyclic compound is2,4-dimercaptopyrimidine.
 7. The electroplating bath of claim 3 whereinthe heterocyclic compound is 2-mercapto-4-amino-6-hydroxypyrimidine. 8.The electroplating bath of claim 3 wherein the heterocyclic compound is5-carboxy-2-mercaptopyridine.
 9. The electroplating bath of claim 3wherein the heterocyclic compound is 3-hydroxy-2-mercaptopyridine. 10.The electroplating bath of claim 3 wherein the heterocyclic is2-mercapto-4,6,-dihydroxypyrimidine.
 11. The electroplating bath ofclaim 3 wherein the heterocyclic compound is 2-thiouracil and thealdehyde is a mixture of anisic aldehyde and vanillin.
 12. Theelectroplating bath of claim 3 wherein the heterocyclic compound is2-mercapto-4,6-dihydroxypyrimidine and the aldehyde is a mixture ofanisic aldehyde and vanillin.
 13. The electroplating bath of claim 2wherein the brightener is an aldehyde having the formula
 14. Theelectroplating bath of claim 13 wherein the aldehyde brightener is abenzaldehyde.
 15. The electroplating bath of claim 13 wherein thealdehyde is vanillin.
 16. The electroplating bath of claim 13 whereinthe aldehyde is anisic aldehyde.
 17. The electroplating bath of claim 13wherein the aldehyde is p-hydroxy-benzaldehyde.
 18. THE ELECTROPLATINGBATH OF CLAIM 1 WHEREIN THE BATH CONTAINS FROM ABOUT 0.01 TO ABOUT 0.2GRAMS PER LITER OF A HETEROCYCLIC COMPOUND SELECTEED FROM THE GROUPCONSISTING OF A 2-MERCAPTO SUBSTITUTED PYRIDINE OR PYRIMIDINE.
 19. Theelectroplating bath of claim 18 wherein the polymeric condensate andheterocyclic compound are present in the bath with the ranges of fromabout 0.3 to about 0.75 and from about 0.025 to about 0.075 grams perliter, respectively.
 20. The electroplating bath of claim 1 wherein thesource of the zinc ions is a water soluble zinc salt.
 21. Theelectroplating bath of claim 20 wherein the zinc salt is zinc sulfate.22. The electroplating bath of claim 1 wherein in the polymericcondensate the dihalopropanol is 1,3-dichloro-2-propanol.
 23. Theelectroplating bath of claim 1 wherein in the polymeric condensate thealkylene polyamine has a tertiary amino group substituted with alkylgroups of from 1 to 5 carbon atoms and the alkylene bridge contains fromabout 2 to about 5 carbon atoms.
 24. The electroplating bath of claim 1wherein in the polymeric condensate the alkylene polyamine isdimethylaminopropylamine.
 25. The electroplating bath of claim 1 whereinin the polymeric condensate the alkylene polyamine isdimethylaminopropylamine and the dihalopropanol is1,3-dichloro-2-propanol and the mol ratio of the polyamine to the1,3-dichloro-2-propanol ranges from about 0.8:1 to about 1.5:1,respectively and the condensate is substantially uncrosslinked.
 26. Theelectroplating bath of claim 1 wherein the polymeric condensate ispresent in the bath within the range of from about 0.3 to about 0.75grams per liter.
 27. The electroplating bath of claim 1 wherein the bathcontains a polyvinyl alcohol within the range of from about 0.02 toabout 0.2 grams per liter.
 28. The electroplating bath of claim 1wherein the pH is above
 14. 29. In a process for the electroplating ofzinc the improvement comprising effecting the electroplating with thealkaline bath of claim 1 free from any cyanide.
 30. The process of claim29 wherein the plating is conducted at a temperature of from about 60*to about 100*F and at a current density of up to 200 amperes per squarefoot.